Paper having a high coefficient of friction



United States Patent Office 3,080,260 Patented Mar. 5, 1963 3,080,260 PAPER HAVING A HIGH COEFFICIENT OF FRICTION Bruce E. Brooks, West Monroe, La., assignor to Olin Mathieson Chemical Corporation, a corporation of Virginia No Drawing. Filed Aug. 5, 1958, Ser. No. 753,202

1 Claim. (Cl. 117152) The present invention relates to cellulosic materials and in particular to kraft paper and kraft paperboard of the type utilized to fabricate bags or paperboard carriers for packaging groups of beer cans, soft drink bottles and the like.

More particularly, the invention relates to paper and paperboard of the above general class wherein the surface of the finished paper has an adherent coating which develops high surface friction.

By the language surface friction" is meant the frictional or slip resistance developed between adjacent sheets of paper or board.

Thus, in a stack of sheets of paper or board which have been manufactured in accordance with the principles of the present invention, the frictional or slip resistance developed between the contact surfaces of adjacent sheet is the characteristic in question here. Paperboard having the adherent coating of the present invention displays a value of slip resistance which represents an increase of as much as 100% over the corresponding value of resistance apparent in untreated paper or board.

For purposes of measuring the relative slip characteristics or the surface frictional resistance between treated and untreated paper, values of resistance are determined as coefficients of static and kinetic friction in any of the several ways described in textbooks of physics. The inclined plane method has proven very satisfactory, the tangent of the angle of inclination of the plane at which a weighted sample of paper or paperboard commences to slide over another sample being numerically equal to the coefiicient of static friction and coefficient of kinetic friction being calculated from the aforesaid angle of inclination and the time required to slide a measured distance.

The succeeding table of data obtained by the above method clearly shows the increased slip resistance or the increased coefficient of friction obtained in the two varieties of paper or board when one compares the values of resistance with and without treating.

TABLE OF DATA Accordingly, it is a special feature of the present invention to provide an improved anti-slip cellulosic material.

Another feature of the invention is the provision of an improved kraft paper including paperboard having an adherent coating developing a high coefiicient of surface friction.

A further feature of the invention is the provision of a kraft paper or board having a coefficient of friction or a slip resistance which can be controlled within the range of about .25 to about .60.

A further feature of the invention is the provision of a paper of the above general class wherein slip resistance has been increased without lowering other attributes of 2 quality in the paper, such as smoothness, appearance, printability, strength and scuff resistance.

A further feature of the invention is the provision of paper and board having an adherent coating comprising a dispersion of finely divided diatomaceous earth; the particle size of the diatomaceous earth being such that about 12% is retained on a 325-mesh screen.

Another feature of the invention is the provision of a paper having an adherent coating developing frictional characteristics which are especially suited for modern material handling and packaging machinery.

A still further feature. of the invention is the provision of kraft paper or board having an adherent starch coating in which finely divided particles of diatomaceous earth have been dispersed.

A cellulosic sheet material having high slip resistance and embracing certain principles of the present invention may include a paper sheet or board having an adherent coating containing diatomaceous earth in amounts ranging from about /2 pound to about 2 pounds per one thousand square feet of surface treated.

Other features and advantages of the invention will be come more apparent from the succeeding specification:

Example I [Used in a single coat starch application] A diatomaceous earth dispersion is prepared in the following formulation, parts and percentages being noted by weight:

40 lbs. Staycol No. 1 brand cornstarch, manufactured by A. E. Staley Mfg. Co. of Decatur, Illinois, or equivalent.

10.3 lbs. carboxy methylcellulose.

1.5 lbs. Calgon brand sodium polyphosphate, manufactured by Calgon, Inc. of Pittsburgh, Pa., or equivalent.

52 lbs. Dicalite brand d-iatornaceous earth, manufactured by Dicalite Department, Great Lakes Carbon Corp, New York, N.Y., or equivalent.

Sufiicient water to make up to 200 gallons.

Example 11 [Utilized in the second coat of a two coat starch application] A diatomaceous earth dispersion is prepared in the following formulation, parts and percentages being noted by weight:

40 lbs. Staycol No. 1 brand cornstarch manufactured by A. E. Staley Mfg. Co. of Decatur, Illinois, or equivalent.

10.3 lbs. Carboxy methylcellulose.

1.0 lb. Calgon brand sodium polyphosphate manufactured by Calgon, Inc. of Pittsburgh, Pa., or equivalent.

64 lbs. Dicalite brand diatomaceous earth, manufactured by Dicalite Department, Great Lakes Carbon Corp, New York, N.Y., or equivalent.

Suflicient water to make up to 200 gallons.

Oviously the amount of diatomaceous earth dispersed may be varied from about 20 parts by weight to about parts by weight consistent with the particular value of slip resistance desired.

Since the invention is not directed to schemes for applying the inherent coating of the present invention, it is deemed suflicient to state that the diatomaceous earth containing dispersion may be applied to the paper in the course of manufacture such as at the size press, the calendar stacks or as a separate operation using suitable rolls, doctor blades, spraying, or painting apparatus.

What is claimed is:

A printable kraft paper having high resistance to slip comprising a sheet of said kraft paper having an adherent coating applied prior to printing containing diatomaceous earth, starch, carbo'xy methylcellulose and polyphosphate, the diatomaceous earth being the friction producing agent the diatomaceous earth being present in said coating in amounts ranging from about V2 pound to about 2 pounds per thousand square feet of kraft paper surface treated, said diatomaceous earth having a particle size such that about 12% is retained on a 325-mesh screen, said kraft paper so treated having a static coefiicient of friction of about .50 and a kinetic coetncient of friction of about .37

References Cited in the file of this patent UNITED STATES PATENTS V Clapp May 10, 1932 ONeil Feb. 5, 1935 4 Codwise May 26, 1936 DeWitt Dec. 19, 1939 Pattilloch Nov. 16, 1954 Schwalbe Jan. 25, 1955 Leptien Feb. 3, 1959 FOREIGN PATENTS OTHER REFERENCES Dicalite Bulletin f-SO, The Dicalite Company, New

York, 1943, page 2.

Quinn et al. Diatomaceous Silica in Paper, Paper Trade Journal, Nov. 2, 1944, pages 12,14and 16. 

